It is known to use a coding pattern to embed some type of information in a passive base such as a sheet of paper, a writing board or equivalent. A suitably programmed scanner, fax machine, camera or digital pen can then read, recreate and use the information embedded locally in the base. For example, graphical information on a base can be supplemented with embedded information which extends the functionality of the base. Such embedded information can comprise file data for full or partial recreation of the graphical information, commands, supplementary text or images, hyperlinks, absolute positions, etc.
Coding patterns are generally constructed around some form of machine-readable code symbols which are regularly spaced on the base. Examples of such coding patterns are given in U.S. Pat. Nos. 5,221,833; 5,477,012; WO 00/73983; WO 01/26032; WO 01/71643; and U.S. Pat. No. 6,330,976.
In many cases, bases with a coding pattern can be generated on a large scale and with high precision in the graphics industry. There are, however, also occasions when it is desirable to create bases with a coding pattern on a small scale. This can then be carried out using a personal computer, to which a printer of, for example, the ink-jet or laser type, has been connected.
This can be carried out in such a way that the required coding pattern is created as an image file in a graphical format, for example, in bitmap format. This image file is converted into a page-describing and normally printer-independent code, such as PostScript (trademark), after which it is transmitted to the printer unit. On the basis of the page-describing code, the printer unit creates corresponding instructions for control of the printer's hardware. This hardware can, in the case of a laser printer, comprise a laser diode with associated optics. In an ink-jet printer, the hardware may comprise an ink ejector. The printing is then carried out on a base, for example a sheet of paper.
If the coding pattern has a high information density, which can be achieved by high information content in each code symbol and/or by dense arrangement of the code symbols on the base, the image file and the page-describing code may become large. Consequently, transfer times and printer processing times for such code may become excessive.
WO 02/082366 proposes a technique to reduce the size of the page-describing code, specifically for a coding pattern that codes a continuous sequence of absolute positions in two dimensions. Here, the printer unit is integrated with a pattern generation module, which is implemented by software and/or hardware to generate the coding pattern based on information describing the boundaries of the absolute positions to be coded on the base. Thus, the page-describing code can be supplemented by such boundary information to represent the coding pattern. This approach provides for significant reduction in both transfer time and printer processing time.
However, it may be difficult or even impossible to upgrade existing printers with the necessary pattern generation module. This may cause a technological barrier to the introduction and adoption of coding patterns on passive bases, since a large number of prospective users must invest in new printers.